A conventional refrigeration air conditioning system having a dehumidifying function is composed of a compressor, a condenser, an expansion valve, an evaporator and a defrost heater. In to a refrigeration cycle of the refrigeration air conditioning system, a refrigerant is filled. The refrigerant compressed by the compressor becomes a high-temperature and high-pressure gas refrigerant and is fed to the condenser. The refrigerant flowing into the condenser becomes a liquid by releasing heat into the air. The liquefied refrigerant is depressurized by the expansion valve to become a gas-liquid two-phase state, and becomes a gas in the evaporator by absorbing heat from the surrounding air to flow into the compressor. Especially, since freezing and cold storage warehouses have to be controlled in a range of temperature below 0° C., the evaporating temperature becomes lower than 0° C. (Generally, in many cases, the inside of freezing and cold storage warehouses is controlled at −10° C. or less.) Because of this, it has happened that frost is generated in the evaporator, which has reduced the cooling performance. Consequently, a heater was mounted on the evaporator and a defrosting operation has been periodically performed. Accordingly, redundant energy has been consumed for defrosting and caused degradation in cooling efficiency of the refrigeration air conditioning system. Moreover, after the defrosting operation, the temperature inside the freezing and cold storage warehouses increased, which caused increasing in the load of the refrigeration air conditioning system and increasing in consumed power.
Hence, a method for eliminating the defrosting operation is disclosed in which a refrigerator and a desiccant rotor as a moisture adsorption means are combined, and moisture in the air flowing into an evaporator (heat absorbing device) is removed in advance by use of such a desiccant rotor that holds an adsorbent such as silica gel, zeolite, or the like on its surface, the adsorbent having a lot of pores having pore sizes of the order of 1.5-2.5 nm and also having a rate of change in equilibrium adsorption amount of moisture in the relative humidity within the range of 30%-60%, which is larger than that in the relative humidity outside the range of 30%-60%.
That is, an adsorbent having a lot of pores such as silica gel, zeolite, or the like is made held on a desiccant rotor, as a moisture adsorption means, and the desiccant rotor is configured to be located across the inside and outside of a freezing room and is rotated at a constant speed. Thereby, the air inside the freezing room is dehumidified by the adsorbent provided on a portion of the desiccant rotor that has moved from the outside of the freezing room to the inside of the freezing room, and the dehumidified air is supplied to an evaporator (heat absorbing device), while the moisture adsorbed by the adsorbent of the desiccant rotor is desorbed to cause the adsorbent to be regenerated through the process that the high temperature air heated by heat discharged from a condenser (radiator) is supplied to a portion of the desiccant rotor that has moved from the inside of the freezing room to an outside-air side space outside the freezing room. Such operations are repeated. (For example, refer to Patent Document 1)    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-46776 (FIG. 2, FIG. 4, FIG. 6, Paragraph 0017-0018, 0024, 0027)